Liquid crystal display mounting structure

ABSTRACT

A LIQUID CRYSTAL DISPLAY MOUNTING STRUCTURE WHEREIN THE ELECTRICAL CONTACTS ON THE BACK SIDE OF A LIQUID CRYSTAL DISPLAY PANEL ARE HELD IN PRESSURE CONTACT WITH A FLAT FLEXIBLE CABLE WHICH PROVIDES ELECTRICAL CONNECTION TO A MATRIX OF DIODES WITHIN A PAIR OF DIODE BOATS OR HOLDERS; INTERCONNECTIONS BETWEEN THE DIODES AND OTHER CIRCUITS ARE PREVIDED BY ETCHED CIRCUIT BOARDS.

c. P. ABBOTT m. ETAL 3,718,842

LIQUID-CRYSTAL DISPLAY MOUNTING S'I'RUTRE Feb. 21, I1973.

` Sheets-Sht l Filed Aprll 2l, 1972- LIQUID CRYSTAL DISPLAY MOUNTINGSTRUCTURE Filed Aprll 2l, 1972 Feb. 27, 1973 c. P. ABBOTT m, ETAL 2Sheets-Sheet 2 United States Patent O 3,718,842 LIQUID CRYSTAL DISPLAYMOUNTING STRUCTURE Charles P. Abbott III, Dallas, and John M. Reilly,Garland, Tex., assignors to Texas Instruments Incorporated,

Dallas, Texf.

Filed Apr. 21, 1972, Ser. No. 246,207 Int. Cl. Hk 1/6'4 U.S. Cl. 317-101CC 4 Claims ABSTRACT OF THE DISCLOSURE A liquid crystal display mountingstructure wherein the electrical contacts on the back side of a liquidcrystal display panel are held in pressure contact with a at exiblecable'which provides electrical connection to a matrix of diodes withina pair of diode boats or holders; interconnections between the diodesand other circuits are provided by etched circuit boards.

The present invention relates to letter-number displays of the typeus'ed to indicate the output or results of instruments such ascalculators, digital voltmeters, counters and the like. Moreparticurlarly, the present invention relates to a mountingvzs'tructurefor mounting a liquid crystal display panel together with the necessaryoperating components to effect, aI visual display.

Modern integrated electronic circuits using large-scale integrationtechniques have made it possible to provide in a single integratedcircuit all of the electronic functions necessary for a' complete systemsuch as, for example, a complete electronic calculator capable ofaddition, subtraction and multiplication and division. Consequently, thesize of such devices is no longer limited by space requirements fortheelectronic components but is limited now by such factors as the spacerequired for batteries or power supplies] the minimum size of inputdevices' such a's keyboards, 'fand output devices such as numericdisplays which will not impair the users eicient operation of the devicebecause of their small size.

Liquid crystal displays are in many ways well suited as output devicesbut until now have been limited in their use partly because ofdiicultie's in making the large number of necessary electricalconnections between the liquid crystal display panel and othercomponents of the system. One liquid crystal display panel now developedis about 2%" long by about 1%0" wide and is capable of displaying ninecharacters with decimal. For such a panel between 75 and 80 electricalcontacts to the panel are required within a space of less than onesquare inch. Previously, individual wires were connected to each contactby hand, the other ends of the Wires being connected to the individualdiodes of a matrix which, in turn, were wired to a connector or etchedcircuit board. Initial assembly as well as repair and replacement ofparts in such an assembly was difficult because of the large number ofconnections and wires in a very limited space.

Therefore, it is one object of the present invention to provide a liquidcrystal display mounting 'structure which is compact and easy andinexpensive to assemble.

It is a further object of the present invention to provide a liquidcrystal display mounting structure which can be readily isassembled tofacilitate repair or replacement of its component parts.

These, together with other objects and advantages will become readilyapparent from the following detailed description and accompanyingdrawings wherein:

PIG. 1 is an exploded view of the mounting structure of. the presentinvention;

3,718,842 Patented Feb. 27., 1973 ice FIG. 1a illustrates an electrodearrangement for dis playing any number from 0 through 9;

FIG. 2 is a view in perspective of the assembled 'structure; and

FIG. 3 is a view in section of the structure taken along lines 3 3 ofFIG. 2.

Illustrated in FIG. 1 is a liquid crystal display panel 10. The panelcomprises a back plate 11 and a front plate 12 which is 'slightly Widerthan the back plate. The plates are separated from each other a shortdistance by a spacer around the periphery of the back plate. Between theplates is a thin cavity tilled with a crystalline liquid of the type nowwell-known. On the inside surfaces of the front and back plates areconductive regions or electrodes which are arranged in patterns andgroups so that numbers or letters are displayed by the panel uponexcitation of the crystalline liquid by application of electricalcurrent to selected ones of the electrodes. Electrical contacts to thevarious electrodes is by means of a conductive lead pattern on the backside of the front plate shown in phantom at 13. Each lead of the patternextends from one of the electrode's within the panel through the sealbetween'the plates to one of the overhanging ledges of the front plate.Two electrical contacts are required for excitation of each segment ofeach ligure of the panel. For example, any of the numerals 0 through 9may be displayed using selective excitation of the electrodes 14arranged as shown in FIG. 1A; one additional electrode 15 may be usedfor a decimal point. Two electrodes are required for each segment of thegure but one of the electrodes may be a common electrode for all of the'segments of a single ligure, usually the back electrode. Thus, it maybe seen that nine contacts are required for each digit of anumerical-decimal display. An eight-digit display panel then requiresseventy two individual connections to the liquid crystal panel.

It can be seen that the area to which electrical contact can'be made toeach of the conductive leads is quite small and that the conductiveleads must be very closely spaced on a panel which has overalldimensions of only 2%" x 1%0". Further, when the panel is to be excitedby a strobing or multiplexing technique, that is, each digit excited inturn sequentially repeatedly for short periods of time, it is oftendesirable or necessary to connect a diode in series with each of thefront electrode segments.

Shown in the figures is the liquid crystal display mounting structure ofthe present invention. As shown, the mounting structure comprises theliquid crystal display panel 10 having a conductive pattern of leads 13on the underside of the top plate, a pair of at flexible cables 14a andb, apair of rubber spacers 16a and b, a pair of diode holders or boats18a and b, a pair of etched circuit boards 20a and b, and a pair ofspring clips 22a andb.

When assembled, the liquid crystal panel 10 rests on top of the flatflexible cables 14 with the metal-lization pattern of the cable inmatching contact with the conductive lead pattern 13 of the liquidcrystal panel. Such at ilexible cables are commercially available or canbe custom-made from a metallized sheet of plastic such as Mylar byetched circuit techniques. Ihe spacers 16 which may be of rubber orother suitable resilient material are positioned under the flexiblecables and rest on the diode boats or holders 18. The diode boats aremade of a suitable insulatirrg material lsuch as phenolic! or insulatingplastic. Small glass diodes 24 are positioned in the holes 26 of theboat holders. Plain wire segments 25 may be used for through connectionswhen diodes are not a circuit requirement. The other ends of the exiblecables have small holes 28 in the leads of the metallization patternarranged to fit over and make contact with the diode leads or wireswhich protrude past the outer surfaces of the diode holders as shown inFIG. 2. Good electrical and structural contact between the diode leadsand the at ilexible cable leads can be achieved either by soldering orby a spot of conductive epoxy glue at each contact. Etched or connectingcircuit Iboards having an appropriate metallization pattern and holepattern are placed against the inner surfaces of the diode boats withthe diode leads extending through the holes in the etched circuit boardas best shown at 30 FIG. 3. The diode leads may `be conductivelyconnected to the circuit board metal pattern by solder or conductiveepoxy glue in the same manner used to connect the diodes to the ilexiblecables. Spring clips 22 hook under each end of each of the diode boatsand over the liquid crystal panel to hold the entire assembly together.

The liquid crystal display assembly can then be mounted by appropriatemeans, such as screws threaded into the bottom surfaces of the diodeboats. As shown in FIG. 2, the display assembly is mounted onto a maincircuit board 32 -by detent fastener 33 leaving room beneath the displayfor the integrated circuits such as shown at 34 which provide theelectronic functions of the system. System interconnections are providedby a metallization pattern on the main circuit board. Electricalconnections between the display assembly and the main circuit board maybe provided through a connector socket (not Shown) in the main circuitboard or by direct connection of the diode leads extending through thedisplay assembly circuit boards to the main circuit board asillustrated.

Thus it can be seen that the display assembly of the present inventioncan lbe easily disassembled for repair and/or replacement of parts.Removal and replacement of the display panel, the part most vulnerableto damage, is especially easy. However, should it be desirable, thedisplay panel connections may be more permanently aiiixed to the leadsof the flat flexible cable by placing a small amount of conductive epoxyglue on each lead of the cable in an area where it is to contact theconductive leads of the display panel before assembly.

Thus, there has been disclosed a new liquid crystal display assemblystructure which is easily and inexpensively constructed and which may beeasily disassembled for repair or replacement of parts. Manymodifications and changes will immediately be obvious to those familiarwith such structures lwhich are still within the spirit and scope of thepresent invention. Therefore, it is intended that this invention belimited only as set forth in the following claims.

What is claimed is:

1. A liquid crystal display assembly comprising:

(a) a liquid crystal display panel having on its back surface aplurality of conductive areas providing electrical access to theinternal electrodes of said panel;

(b) a pair of flat ileXible multiconductor cables having the conductorsat at least one end spaced for a matching relationship between theconductors and respective conductive areas of said panels;

(c) a pair of resilient spacer members;

(d) a pair of rigid component holders having cavities therein adapted tosupport a plurality of components in iixed space relationship to oneanother with electrical leads of said components extending from oppositefaces of said holders;

(e) a pair of connecting circuit boards, each having a pattern of holestherein in a pattern matching said cavities of said component holders;

(f) a plurality of circuit components positioned in the cavities of saidcomponent holders; and

(g) a pair of spring clips holding the foregoing elements in assemblythrough engagement of each clip with the top of said panel at one endand the underside of each of said component holders at one end thusurging said component holder, said spacer and said at cable against saidpanel with the conductors of said cable making electrical contact withrespective conductive areas of said panel, the other ends of saidconductors being connected to leads of said components, the other leadsof said components being attached to said connecting circuit boardspositioned against the faces of said component holders.

2. The liquid crystal display assembly as defined in claim 1 whereinsaid components comprise diodes and WlIeS.

3. The liquid crystal display assembly of claim 1 wherein the conductorsof said flat flexible cable are axed to respective conductive areas ofsaid panel by conductive epoxy glue.

4. The liquid crystal display assembly of claim 1 wherein saidconnecting circuit boards have conductive paths thereon providingelectrical interconnection between selected ones of said components.

References Cited UNITED STATES PATENTS 3,161,867 12/1964 Isborn Z50-213A 3,340,437 9/1967 Fricker, Jr 317-101 CW 3,505,570 4/1970 Sprude et al317--101 CW 3,638,033 l/l972 Johnson et al. 339-176 MP DAVID SMITH, J R,Primary Examiner U.S. Cl. X.R.

